#define _CRT_SECURE_NO_WARNINGS
#include"stdio.h"
int fib(int n) {
	if (n <= 2)
		return 1;
	else
		return fib(n - 1) + fib(n - 2);
}
int main() {
	int n = 0;
	scanf("%d", &n);
	int ref = fib(n);
	printf("%d\n", ref);
	return 0;
}